I can comment a bit here as I live in Belgium and my father was working for bpost not so long ago as a business analyst on the support part.
The company (I think we can call it a company, it's not a public service anymore) had to operate a switch on their core business. As the volume of letters and postal cards kept getting lower and lower and packets were slightly up, they had to change their focus.
Packets generally mean fast delivery, in Belgium and international with great tracking solutions.
For their tracking page, they are using a .cloud domain (track.bpost.cloud)
Now getting the .com could probbaly help them to go international (mainly for corporate customers, individuals won't be affected too much), it would help to gain trust too probably if switching away from .cloud
Could bpost have bought the domain from the current owner?
Possible. This year, bpost investors won't receive any dividend. The company stats were impacted by the current crisis but the results were still better than hoped so the stock value increased (no loss).
Now for bpost, spending money on a domain might not be the best investment at the moment.
Competition is high for packets.
As for the RDNH question, I'm not sure exactly. Bpost has not always been called bpost, the name was introduced a few years ago, before it was just "the post", it could have an impact on the resolution of this WIPO case.